/* mpicoder.c - Coder for the external representation of MPIs * Copyright (C) 1998, 1999, 2000, 2001, 2002, * 2003 Free Software Foundation, Inc. * * This file is part of Libgcrypt. * * Libgcrypt is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * Libgcrypt is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include #include #include #include #include #include "mpi-internal.h" #include "g10lib.h" #define MAX_EXTERN_MPI_BITS 16384 static gcry_mpi_t mpi_read_from_buffer(byte *buffer, unsigned *ret_nread, int secure) { int i, j; unsigned int nbits, nbytes, nlimbs, nread=0; mpi_limb_t a; gcry_mpi_t val = MPI_NULL; if( *ret_nread < 2 ) goto leave; nbits = buffer[0] << 8 | buffer[1]; if( nbits > MAX_EXTERN_MPI_BITS ) { log_error("mpi too large (%u bits)\n", nbits); goto leave; } else if( !nbits ) { log_error("an mpi of size 0 is not allowed\n"); goto leave; } buffer += 2; nread = 2; nbytes = (nbits+7) / 8; nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB; val = secure? mpi_alloc_secure( nlimbs ) : mpi_alloc( nlimbs ); i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; i %= BYTES_PER_MPI_LIMB; j= val->nlimbs = nlimbs; val->sign = 0; for( ; j > 0; j-- ) { a = 0; for(; i < BYTES_PER_MPI_LIMB; i++ ) { if( ++nread > *ret_nread ) log_bug("mpi larger than buffer"); a <<= 8; a |= *buffer++; } i = 0; val->d[j-1] = a; } leave: *ret_nread = nread; return val; } /**************** * Make an mpi from a hex character string. */ static int mpi_fromstr(gcry_mpi_t val, const char *str) { int sign=0, prepend_zero=0, i, j, c, c1, c2; unsigned nbits, nbytes, nlimbs; mpi_limb_t a; if( *str == '-' ) { sign = 1; str++; } /* skip optional hex prefix */ if ( *str == '0' && str[1] == 'x' ) { str += 2; } nbits = strlen(str)*4; if( nbits % 8 ) prepend_zero = 1; nbytes = (nbits+7) / 8; nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB; if( val->alloced < nlimbs ) mpi_resize(val, nlimbs ); i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; i %= BYTES_PER_MPI_LIMB; j= val->nlimbs = nlimbs; val->sign = sign; for( ; j > 0; j-- ) { a = 0; for(; i < BYTES_PER_MPI_LIMB; i++ ) { if( prepend_zero ) { c1 = '0'; prepend_zero = 0; } else c1 = *str++; assert(c1); c2 = *str++; assert(c2); if( c1 >= '0' && c1 <= '9' ) c = c1 - '0'; else if( c1 >= 'a' && c1 <= 'f' ) c = c1 - 'a' + 10; else if( c1 >= 'A' && c1 <= 'F' ) c = c1 - 'A' + 10; else { mpi_clear(val); return 1; } c <<= 4; if( c2 >= '0' && c2 <= '9' ) c |= c2 - '0'; else if( c2 >= 'a' && c2 <= 'f' ) c |= c2 - 'a' + 10; else if( c2 >= 'A' && c2 <= 'F' ) c |= c2 - 'A' + 10; else { mpi_clear(val); return 1; } a <<= 8; a |= c; } i = 0; val->d[j-1] = a; } return 0; } /* Dump the value of A in a format suitable for debugging to Libgcrypt's logging stream. Note that one leading space but no trailing space or linefeed will be printed. It is okay to pass NULL for A. */ void gcry_mpi_dump (const gcry_mpi_t a) { int i; log_printf (" "); if (!a) log_printf ("[MPI_NULL]"); else { if (a->sign) log_printf ( "-"); #if BYTES_PER_MPI_LIMB == 2 # define X "4" #elif BYTES_PER_MPI_LIMB == 4 # define X "8" #elif BYTES_PER_MPI_LIMB == 8 # define X "16" #elif BYTES_PER_MPI_LIMB == 16 # define X "32" #else # error please define the format here #endif for (i=a->nlimbs; i > 0 ; i-- ) { log_printf (i != a->nlimbs? "%0" X "lX":"%lX", (ulong)a->d[i-1]); } #undef X if (!a->nlimbs) log_printf ("0"); } } /* Convience function used internally. */ void _gcry_log_mpidump (const char *text, gcry_mpi_t a) { log_printf ("%s:", text); gcry_mpi_dump (a); log_printf ("\n"); } /**************** * Return an m_alloced buffer with the MPI (msb first). * NBYTES receives the length of this buffer. Caller must free the * return string (This function does return a 0 byte buffer with NBYTES * set to zero if the value of A is zero. If sign is not NULL, it will * be set to the sign of the A. */ static byte * do_get_buffer( gcry_mpi_t a, unsigned *nbytes, int *sign, int force_secure ) { byte *p, *buffer; mpi_limb_t alimb; int i; size_t n; if( sign ) *sign = a->sign; *nbytes = a->nlimbs * BYTES_PER_MPI_LIMB; n = *nbytes? *nbytes:1; /* allocate at least one byte */ p = buffer = force_secure || mpi_is_secure(a) ? gcry_xmalloc_secure(n) : gcry_xmalloc(n); for(i=a->nlimbs-1; i >= 0; i-- ) { alimb = a->d[i]; #if BYTES_PER_MPI_LIMB == 4 *p++ = alimb >> 24; *p++ = alimb >> 16; *p++ = alimb >> 8; *p++ = alimb ; #elif BYTES_PER_MPI_LIMB == 8 *p++ = alimb >> 56; *p++ = alimb >> 48; *p++ = alimb >> 40; *p++ = alimb >> 32; *p++ = alimb >> 24; *p++ = alimb >> 16; *p++ = alimb >> 8; *p++ = alimb ; #else #error please implement for this limb size. #endif } /* this is sub-optimal but we need to do the shift oepration because * the caller has to free the returned buffer */ for(p=buffer; !*p && *nbytes; p++, --*nbytes ) ; if( p != buffer ) memmove(buffer,p, *nbytes); return buffer; } byte * _gcry_mpi_get_buffer( gcry_mpi_t a, unsigned *nbytes, int *sign ) { return do_get_buffer( a, nbytes, sign, 0 ); } byte * _gcry_mpi_get_secure_buffer( gcry_mpi_t a, unsigned *nbytes, int *sign ) { return do_get_buffer( a, nbytes, sign, 1 ); } /**************** * Use BUFFER to update MPI. */ void _gcry_mpi_set_buffer( gcry_mpi_t a, const byte *buffer, unsigned nbytes, int sign ) { const byte *p; mpi_limb_t alimb; int nlimbs; int i; nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB; RESIZE_IF_NEEDED(a, nlimbs); a->sign = sign; for(i=0, p = buffer+nbytes-1; p >= buffer+BYTES_PER_MPI_LIMB; ) { #if BYTES_PER_MPI_LIMB == 4 alimb = *p-- ; alimb |= *p-- << 8 ; alimb |= *p-- << 16 ; alimb |= *p-- << 24 ; #elif BYTES_PER_MPI_LIMB == 8 alimb = (mpi_limb_t)*p-- ; alimb |= (mpi_limb_t)*p-- << 8 ; alimb |= (mpi_limb_t)*p-- << 16 ; alimb |= (mpi_limb_t)*p-- << 24 ; alimb |= (mpi_limb_t)*p-- << 32 ; alimb |= (mpi_limb_t)*p-- << 40 ; alimb |= (mpi_limb_t)*p-- << 48 ; alimb |= (mpi_limb_t)*p-- << 56 ; #else #error please implement for this limb size. #endif a->d[i++] = alimb; } if( p >= buffer ) { #if BYTES_PER_MPI_LIMB == 4 alimb = *p-- ; if( p >= buffer ) alimb |= *p-- << 8 ; if( p >= buffer ) alimb |= *p-- << 16 ; if( p >= buffer ) alimb |= *p-- << 24 ; #elif BYTES_PER_MPI_LIMB == 8 alimb = (mpi_limb_t)*p-- ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 8 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 16 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 24 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 32 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 40 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 48 ; if( p >= buffer ) alimb |= (mpi_limb_t)*p-- << 56 ; #else #error please implement for this limb size. #endif a->d[i++] = alimb; } a->nlimbs = i; assert( i == nlimbs ); } /* Convert the external representation of an integer stored in BUFFER with a length of BUFLEN into a newly create MPI returned in RET_MPI. If NBYTES is not NULL, it will receive the number of bytes actually scanned after a successful operation. */ gcry_error_t gcry_mpi_scan( struct gcry_mpi **ret_mpi, enum gcry_mpi_format format, const unsigned char *buffer, size_t buflen, size_t *nscanned ) { struct gcry_mpi *a = NULL; unsigned int len; int secure = (buffer && gcry_is_secure (buffer)); if (format == GCRYMPI_FMT_SSH) len = 0; else len = buflen; if( format == GCRYMPI_FMT_STD ) { const byte *s = buffer; a = secure? mpi_alloc_secure ((len+BYTES_PER_MPI_LIMB-1) /BYTES_PER_MPI_LIMB) : mpi_alloc ((len+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); if( len ) { /* not zero */ a->sign = *s & 0x80; if( a->sign ) { /* FIXME: we have to convert from 2compl to magnitude format */ mpi_free(a); return gcry_error (GPG_ERR_INTERNAL); } else _gcry_mpi_set_buffer( a, s, len, 0 ); } if( ret_mpi ) { mpi_normalize ( a ); *ret_mpi = a; } else mpi_free(a); return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_USG ) { a = secure? mpi_alloc_secure ((len+BYTES_PER_MPI_LIMB-1) /BYTES_PER_MPI_LIMB) : mpi_alloc ((len+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); if( len ) /* not zero */ _gcry_mpi_set_buffer( a, buffer, len, 0 ); if( ret_mpi ) { mpi_normalize ( a ); *ret_mpi = a; } else mpi_free(a); return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_PGP ) { a = mpi_read_from_buffer( (char*)buffer, &len, secure); if( nscanned ) *nscanned = len; if( ret_mpi && a ) { mpi_normalize ( a ); *ret_mpi = a; } else mpi_free(a); return gcry_error (a ? GPG_ERR_NO_ERROR : GPG_ERR_INV_OBJ); } else if( format == GCRYMPI_FMT_SSH ) { const byte *s = buffer; size_t n; if( len && len < 4 ) return gcry_error (GPG_ERR_TOO_SHORT); n = s[0] << 24 | s[1] << 16 | s[2] << 8 | s[3]; s += 4; if (len) len -= 4; if( len && n > len ) return gcry_error (GPG_ERR_TOO_LARGE); /* or should it be too_short */ a = secure? mpi_alloc_secure ((n+BYTES_PER_MPI_LIMB-1) /BYTES_PER_MPI_LIMB) : mpi_alloc ((n+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); if( n ) { /* not zero */ a->sign = *s & 0x80; if( a->sign ) { /* FIXME: we have to convert from 2compl to magnitude format */ mpi_free(a); return gcry_error (GPG_ERR_INTERNAL); } else _gcry_mpi_set_buffer( a, s, n, 0 ); } if( nscanned ) *nscanned = n+4; if( ret_mpi ) { mpi_normalize ( a ); *ret_mpi = a; } else mpi_free(a); return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_HEX ) { if( buflen ) return gcry_error (GPG_ERR_INV_ARG); /* can only handle C strings for now */ a = secure? mpi_alloc_secure (0) : mpi_alloc(0); if( mpi_fromstr( a, buffer ) ) return gcry_error (GPG_ERR_INV_OBJ); if( ret_mpi ) { mpi_normalize ( a ); *ret_mpi = a; } else mpi_free(a); return gcry_error (GPG_ERR_NO_ERROR); } else return gcry_error (GPG_ERR_INV_ARG); } /* Convert the big integer A into the external representation described by FORMAT and store it in the provided BUFFER which has been allocated by the user with a size of BUFLEN bytes. NWRITTEN receives the actual length of the external representation unless it has been passed as NULL. BUFFER may be NULL to query the required length.*/ gcry_error_t gcry_mpi_print( enum gcry_mpi_format format, unsigned char *buffer, size_t buflen, size_t *nwritten, struct gcry_mpi *a) { unsigned int nbits = mpi_get_nbits(a); size_t len; size_t dummy_nwritten; if (!nwritten) nwritten = &dummy_nwritten; len = buflen; *nwritten = 0; if( format == GCRYMPI_FMT_STD ) { char *tmp; int extra = 0; unsigned int n; if( a->sign ) return gcry_error (GPG_ERR_INTERNAL); /* can't handle it yet */ tmp = _gcry_mpi_get_buffer( a, &n, NULL ); if( n && (*tmp & 0x80) ) { n++; extra=1; } if (buffer && n > len) { gcry_free(tmp); return gcry_error (GPG_ERR_TOO_SHORT); /* the provided buffer is too short */ } if( buffer ) { byte *s = buffer; if( extra ) *s++ = 0; memcpy( s, tmp, n-extra ); } gcry_free(tmp); *nwritten = n; return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_USG ) { unsigned int n = (nbits + 7)/8; /* we ignore the sign for this format */ /* FIXME: for performance reasons we should put this into * mpi_aprint becuase we can then use the buffer directly */ if (buffer && n > len) return gcry_error (GPG_ERR_TOO_SHORT); /* the provided buffer is too short */ if( buffer ) { char *tmp; tmp = _gcry_mpi_get_buffer( a, &n, NULL ); memcpy( buffer, tmp, n ); gcry_free(tmp); } *nwritten = n; return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_PGP ) { unsigned int n = (nbits + 7)/8; if( a->sign ) return gcry_error (GPG_ERR_INV_ARG); /* pgp format can only handle unsigned */ if (buffer && n+2 > len) return gcry_error (GPG_ERR_TOO_SHORT); /* the provided buffer is too short */ if( buffer ) { char *tmp; byte *s = buffer; s[0] = nbits >> 8; s[1] = nbits; tmp = _gcry_mpi_get_buffer( a, &n, NULL ); memcpy( s+2, tmp, n ); gcry_free(tmp); } *nwritten = n+2; return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_SSH ) { char *tmp; int extra = 0; unsigned int n; if( a->sign ) return gcry_error (GPG_ERR_INTERNAL); /* can't handle it yet */ tmp = _gcry_mpi_get_buffer( a, &n, NULL ); if( n && (*tmp & 0x80) ) { n++; extra=1; } if (buffer && n+4 > len) { gcry_free(tmp); return gcry_error (GPG_ERR_TOO_SHORT); /* the provided buffer is too short */ } if( buffer ) { byte *s = buffer; *s++ = n >> 24; *s++ = n >> 16; *s++ = n >> 8; *s++ = n; if( extra ) *s++ = 0; memcpy( s, tmp, n-extra ); } gcry_free(tmp); *nwritten = 4+n; return gcry_error (GPG_ERR_NO_ERROR); } else if( format == GCRYMPI_FMT_HEX ) { byte *tmp; int i; int extra = 0; unsigned int n=0; tmp = _gcry_mpi_get_buffer( a, &n, NULL ); if( !n || (*tmp & 0x80) ) extra=2; if(buffer && 2*n + extra + !!a->sign + 1 > len) { gcry_free(tmp); return gcry_error (GPG_ERR_TOO_SHORT); /* the provided buffer is too short */ } if( buffer ) { byte *s = buffer; if( a->sign ) *s++ = '-'; if( extra ) { *s++ = '0'; *s++ = '0'; } for(i=0; i < n; i++ ) { unsigned int c = tmp[i]; *s++ = (c >> 4) < 10? '0'+(c>>4) : 'A'+(c>>4)-10 ; c &= 15; *s++ = c < 10? '0'+c : 'A'+c-10 ; } *s++ = 0; *nwritten = s - buffer; } else { *nwritten = 2*n + extra + !!a->sign + 1; } gcry_free(tmp); return gcry_error (GPG_ERR_NO_ERROR); } else return gcry_error (GPG_ERR_INV_ARG); } /**************** * Like gcry_mpi_print but this function allocates the buffer itself. * The caller has to supply the address of a pointer. NWRITTEN may be * NULL. */ gcry_error_t gcry_mpi_aprint( enum gcry_mpi_format format, unsigned char **buffer, size_t *nwritten, struct gcry_mpi *a ) { size_t n; gcry_error_t rc; *buffer = NULL; rc = gcry_mpi_print( format, NULL, 0, &n, a ); if( rc ) return rc; *buffer = mpi_is_secure(a) ? gcry_xmalloc_secure( n ) : gcry_xmalloc( n ); rc = gcry_mpi_print( format, *buffer, n, &n, a ); if( rc ) { gcry_free(*buffer); *buffer = NULL; } else if( nwritten ) *nwritten = n; return rc; }